Step 14: Final Comments

It may look strange to build an electronics project without a circuit board in this open wiring style. Old timers called it "rats nest" wiring, but despite the negative term it's perfectly OK.

If you construct it right, the wiring has enough strength to stand on its own and the box provides adequate shielding.I've used my mixers in the car and elsewhere with no problems for several years.

However, if you're worried about the open wiring, then you can always cover the bare wires & resistors with electricians tape, just make sure not to break something in the process. 

If you really wanted to make the mixer super rugged, you could fill the tin with epoxy, parafin or circuit-grade Silicone RTV.

Note: Don't use the regular Silicone RTV made for caulking and bathroom sealer. This stuff gives off acetic acid which will eat through your wires and ruin your project after a while. Circuit-grade Silicone RTV does not give off acid and is safe for wiring. I've read that GE Silicone II (available at home improvement stores) does not leach acid and also silicone RTV sold at automotive part stores labeled either 'Oxygen-sensor Safe' or 'Type B' should be OK.

I hope you are successful and get lots of good use out of this project, please let me know.



<p>Made one!!<br>It was my first time soldering something.<br>I kinda screwed up half way and now the wires are crossing each other... but it works!!<br>If you have any constructive criticism, please shot it at me!!</p>
Hey, it looks great! I like they way you mixed 1/4&quot; and 1/8&quot; connectors. No real constructive criticisms, if it works, that's the real test. I'm not sure Jimi Hendrix' head was that square but otherwise looks great (jk ;^) -- Rich
Made one and it works great. Thanks.
Wow, really nice job! Good idea to use resistor networks!<br /> <br /> Would you care to share the artwork?<br />
Jacks are Mouser 161-3508-E. Resistor networks are Mouser 652-4608X-1LF-1K 1k ohm. Other resistor values are available. Board was fabricated by ExpressPCB.com.
Can this image be used to have a board made or do we need the ExpressPCB file?
This is a 2 sided board and I don't know if the image is scaled correctly once you download it. I do have the ExpressPCB file if you want it. Email me at steve&quot;at&quot;PowerSwitchTail&quot;dot&quot;com.
<p>I noticed the connection to ground on both resistor arrays (last but one pin). The &quot;rats' nest&quot; desing seems to omit that. Could you explain why it matters?</p>
<p>The circuit board layout is chipmonger's and while I see what you mean, I don't know why he choose to tie those 2 resistors to ground -- I can't see that it serves any necessary function (also doesn't hurt anything). The resistor network he's using contains 8 resistors with a value of 1k Ohm each, all tied together on one side and connected to pin 1 (output signal in this case). Pins 2-9 are the other side of each resistor, which chipmonger is using as mixer inputs. He could've done 8 inputs, but only did 4, and needed one network for each stereo channel (L + R). So again, no idea why he choose to do that, but maybe he'll reply. Guaranteed it's not necessary though.</p>
<p>Thanks a lot for the answer, I could not figure out its role either. Current would flow that way (i think) when an input is present, but there's nothing plugged into the output? I guess I'll build it as is and then make some measurments with a multimeter.</p>
Looks like a 2-sided board with the silkscreen mask drawn in so you would either need the file or just reproduce it on your own. It isn't mine and I don't have it. Maybe chipmonger would nice enough to provide if you asked.
Thanks for the artwork and again, really nice job!
<p>why did you put the resistors , can we do it with out them ?</p>
Please read FAQ on step 15. You can do anything you like, but unless you want to use this as a signal splitter, leaving out the resistors is a bad idea.
<p>It works!!!</p>
Hah! that's a crazy-looking tin, I like it! Good job, glad it worked.<br><br>Rich
I made a new passive mixer based on your ible. Thank you so much for the awesome instructions !
<p>that I can use my PC headphone output as input 1 &amp; a low level source as input 2? I know PC output is amplified, but thought you may have any suggestion. I know I can use car audio HI-Low adapter, but like to use your idea for a compact box, Thanks </p>
I would suggest just trying it first, if there is too big a difference in the input levels, you may need to lower the resistor values for the low level signal. You can do this either by replacing the resistors or by soldering resistors in parallel. The formula for the resulting resistance is (r1 x r2)/(r1 + r2)<br><br> Good luck
Great box! Thanks for sharing the pictures!<br> <br> Rich
<p>This was exactly what I was looking for. Thank you for making the instructions clear and actually including a circuit diagram that wasn't made in MS Paint. It works perfectly for what I need, and every input comes out the other end crystal clear, even when multiple sources are playing at once.</p><p>I ended up using a Radioshack project box instead of an Altoids tin, mostly because I just didn't have one sitting around and the box was actually cheaper than a tin of Altoids. This also makes the drilling significantly easier and prevents any unintentional shorts. </p><p>Thank you again for taking the time to make this useful, clear and concise guide.</p>
Hey, nice job! Glad you were successful and thanks for posting the pictures!
<p>works pretty nice! great idea!!!</p>
<p>Nice job! I like the jacks you used, where did you get them?</p><p>Rich</p>
<p>hi from Germany. I found the Jacks at www.conrad.de but I will make an other one with 6,2mm jacks :-)</p>
<p>thanks for the great idea! I did a mixer/splitter for an experimental music project</p>
<p>Hey Vanderaalle, great job!! Looks like you're using 1/4&quot; jacks and I *love* the tin (although not a smoker myself). Hope this works well for you.</p><p>-Rich</p>
I made mine. Not as pretty as yours but sure gets the job done! Stuck with the 1k resistors. Thanks for the great 'structable!
Thanks for posting. Here is my version,&nbsp;it works perfectly.<br> <br> C3-PO is an old ball mouse. After removing the guts there was plenty of room for the wiring. For the triple input audio jack I used parts from an old motherboard's sound card. They have five leads on each; 1) ground, 2) closed tip, 3) open tip, 4) closed ring, 5) open ring. When a plug is inserted, the part that touches the tip moves from the open tip lead to the closed tip lead. This must be how a computer knows when a plug is inserted. I used the closed tip/ring leads, leaving the open/tip leads alone. I wonder if the the open leads could be used for anything.
Nice! Good recycling!
Thank you. I used pulled parts from trashed sound card and a &quot;Smalls&quot; tin.... I love Old school point-to-point wiring...and Hot glue.
Here's my version of the mixer, using a Lucky Stars Candy tin. I plan to add a &quot;floor&quot; above the wiring so that I can store a short 1/8&quot; patch cord inside as well.
Nice! I particularly like the 'Hello Kitty' motif ;^) Thanks for sharing the picture.<br><br>Rich
Made one in less than an two hours, including trip to radio shack for parts, and safeway for MINI altoids tin. Used 1k resistors. Very Small, works fine.
Nice job!<br> <br> Good idea to run the connectors out of the bottom of the mini altoids tin.<br> <br> Looks like you used heat-shrink tubing for insulation as well. Heat-shrink is one of the best things ever for building things and professional wiring repairs.<br> <br> I'm glad it worked for you and thanks for sharing the picture.<br> <br> - Rich
<p>Looks like you have 4.7K resistors in the pictures and 1K resistors in the parts list. Which works better?</p>
Honestly, it's not that critical as long as they're all the same value. Lower resistor values will result in less signal loss, but at some point there will start to be some degree of distortion (when you start to get down below 10x the output impedance of the devices, for example), but that depends on a lot of factors. I think 1K ohm is plenty high enough and you could probably get away with half that -- say 470 ohms or higher, and be fine.
Made one in 5 min today. Looked online and I only found one that would have run me $75. I had most of the parts (missing another audio jack). Works great and i can add the jack later.
<p>Thank you Rich!</p><p> This solved sooo many issues I was trying to maneuver around.</p><p> My '07 E90 BMW (3 series) came without Bluetooth and USB features but thank goodness for the Aux input! This solution allows me to use my external navigation(which doubles as a USB input for music) and a separate external Bluetooth hands-free unit simultaneously through the audio system!</p><p> I chose a smaller tin which fits perfectly into the arm rest compartment, where the Aux input is. I placed the stereo jacks on the lid facing upwards for easy access and compact setup. </p><p> The internal wiring is conceptually the same as you've advised, just arranged differently. I also used 1mm heat shrink tubes to cover up the resistor leads. High quality 1% 1/8W metal film resistors with flame retardant coating were used. </p><p> An upgrade to an OEM <br>Bluetooth/USB upgrade head unit is not only costly, it would force me to <br>choose one among Bluetooth, USB and Aux inputs, whereas I want to use all sources/options as I choose, independently. For example, an OEM Bluetooth/USB upgrade head unit <br>would shut off all other audio when taking a call, whereas I want to be <br>able to hear the navigation (as well as music if I choose) while taking a call.</p><p> Again, thank you! Cheers!</p>
<p>Hell yeah! I made it for my volcas, and it works. Very simple and great solution, thanks!</p>
made one this eve. FUN! thank you for the clear instructions .
<p>Made it with this cute tin - difficult to drill the holes. Thanks for the instructions. I don't find there's any need to connect the grounds other than through the tin.</p>
<p>Made one! and works :)</p>
<p>i made one and combined it with the CMOY headphone amp. Works great with my Volcas! Thank you for this tutorial!<br>Girlfriend's BodyShop body lotion container works great as case. It also smell good ;-) </p>
<p>Thanks for the great write-up! I have a question expanding upon the Step 16 Variation. I want to set up a connection between my gaming console, headset, and an aux input for music. The idea would be to have the aux input feed music to the headset along with the game sound and chat. I would likely adjust the source volumes to balance these two. In addition to that, I want the aux input to mix into my mic input. The purpose of this is to play music while in party chat so everyone in my party can listen. I modified your schematic a bit to show what I mean. I know the mic is a low level input; could a larger resistor be placed on the aux input to the mic to balance these so the mic is not drowned out? Also, is there a component that keep my game sound from being sent to the mic? Looked through most of the comments but couldn't find any that addressed this specifically. Please let me know what you think - thanks!</p>
Resistor to ground gives more consistent mixing when used with different amplifiers.
Thanks for explaining your reasoning. I see your point, you're providing a more constant load to your inputs regardless of the load the output is driving, but it's at the cost of reducing your signal further. I'm not convinced it's going to give you a noticeable improvement, but other than the signal reduction due to the voltage divider, it won't hurt anything -- matter of preference I guess. As I said to Huszko, it might be nice to split the 8 resistors up so each input had the option of going through 2 resistors in parallel (jumper selectable) so you could give an effective 'boost' to selected inputs by halving the input impedance. In any case, again, nice job on your board!
One end of the resistor network is tied to ground to form a reference point for the passive mixer. This is necessary for the mixer to work with various amplifier inputs.
<p>I made it and it works like a charm thank you for the awesome instructions!</p>
<p>Hey, I want to build a mixer for the same purpose. But I need also a Cinch Input. Do you think, that it is possible to at something like that? </p>

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